A 10-Year Cloud Fraction Climatology of Liquid Water Clouds over Bern Observed by a Ground-Based Microwave Radiometer

Remote Sensing

Federico Cossu¹  Klemens Hocke¹  Christian Mätzler¹  Alexander A. Kokhanovsky² 

[1] Institute of Applied Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland; E-Mails:Institute of Applied Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland;

关键词: microwave radiometer;    integrated cloud liquid water;    liquid water path;    cloud fraction;    climatology;    diurnal cycle;    mid-latitudes;    Bern;    TROWARA;   

DOI  :  10.3390/rs70607768

来源: mdpi

【 摘 要 】

Cloud fraction (CF) is known as the dominant modulator of Earth’s radiative fluxes. Ground-based CF observations are useful to characterize the cloudiness of a specific site and are valuable for comparison with satellite observations and numerical models. We present for the first time CF statistics (relative to liquid clouds only) for Bern, Switzerland, derived from the observations of a ground-based microwave radiometer. CF is derived with a new method involving the analysis of the integrated liquid water distribution measured by the radiometer. The 10-year analyzed period (2004–2013) allowed us to compute a CF climatology for Bern, showing a maximum CF of 60.9% in winter and a minimum CF of 42.0% in summer. The CF monthly anomalies are identified with respect to the climatological mean values, and they are confirmed through MeteoSwiss yearly climatological bulletins. The CF monthly mean variations are similar to the observations taken at another Swiss location, Payerne, suggesting a large-scale correlation between different sites on the Swiss Plateau. A CF diurnal cycle is also computed, and large intraseasonal variations are found. The overall mean CF diurnal cycle, however, shows a typical sinusoidal cycle, with higher values in the morning and lower values in the afternoon.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland